This invention relates to an improvement in a spring driven timer motor, of the type, for example, described in U.S. Pat. No. 4,135,474. More specifically, this invention relates to an improved mechanism for disengaging the winding shaft of the timer from positive, driving engagement with at least that segment of the timer's drive train including the governor during winding of the timer.
A spring wound timer motor must have a governor included in its drive train in order to slow the unwinding of the timer's spring sufficiently that the timer operates to measure a desired interval of time. The inertial and frictional resistance exerted by such a governor is so great, however, as to make the required manual winding of the drive spring for actuation of the timer exceedingly difficult. Moreover, it is usually desired that during winding of the motor, no other movement in the motor occur. Consequently, it is conventional in such a timer to provide a mechanism for disengaging the winding shaft of the timer, to which the torque of the coiled drive spring is directly transmitted by connection of one end of the spring to the shaft together with connection of the other end of the spring to the timer housing, from at least that segment of the timer's drive train including the governor during winding of the timer. Such a mechanism may conveniently be called a "clutch."
One such clutch mechanism is illustrated in the aforementioned U.S. Pat. No. 4,135,474. In particular, the shaft 24c of a member 24 of the gear train is journalled at its ends in identical, substantially vertical slots in opposed walls of the timer housing. The spring 20 exerts upon the gear 22, which is fixed to the shaft which the spring 20 drives, a counterclockwise torque (as viewed in FIG. 2 of the aforementioned patent), whereby part 23, including a combined gear 23a and pinion 23b, has a clockwise torque imparted to it. The application to the part 24, which includes a combination of a gear 24a and a pinion 24b, of the clockwise torque of the part 23 not only imparts a counterclockwise torque to the part 24 but also urges the part 24 upwardly so that the shaft 24c thereof bears against the upper extremity of the aforementioned slot. In this position, the pinion 24b is in positive driven engagement with the gear 23a and the gear 24a is in positive driving engagement with a pinion 25b of a governor mechanism also including a star wheel 25a and a governor 26. Upon manual clockwise rotating of a gong bell 16 or a handle 13a in order to wind the timer, all the aforementioned torque directions are correspondingly reversed, whereupon the gear 24a moves out of driving engagement with the pinion 25b, the shaft 24c sliding toward the other end of the aforementioned slot in which it is journalled. Permitting the spring to unwind after the winding operation brings the gear 24a into driving engagement with the pinion 25b again.
The above described prior art arrangement has certain disadvantages. The shaft of the part which shifts must be journalled in slots in opposed walls of the housing so that design of the timer always requires that a continuous clear space be provided between the walls of the housing for receiving the shaft. The slots must be shifted it is desired to have the timer be actuated by winding in the opposite direction from the original design, which means that two sets of tooling for the housing walls are needed. Generally, it is not practical to take power off the shaft which shifts, further limiting the flexibility of application of the timer.
Other prior art arrangements which might be considered sufficiently pertinent to warrant comparison with the present invention but with respect to which the present invention is patentably distinct are as follows.
U.S. Pat. No. 2,601,908 discloses a motor for toys in which on releasing the winding key 20 to allow the spring to unwind, the toothed wheel 23, through the pinion 22, lifts the axle 12 for its gear wheel to engage with and rotate the pinion 24.
U.S. Pat. No. 3,202,006 discloses a rotating mechanism for a plating barrel in which there is used an idler gear between a drive gear and a driven gear on the barrel, the idler gear being mounted in such a way that it can move freely toward and away from drive transmitting relation between the drive and driven gears. The idler gear is held in mesh with the drive and driven gears by the forces which the latter two gears themselves exert on the idler gear. As wear occurs, the idler gear shifts automatically under these forces to take up the slack which would otherwise occur.
It is an object of the present invention to provide a clutch mechanism for a spring wound timer motor which avoids the disadvantages of the prior art.
Other objects and advantages of the invention will be apparent from the following description of the invention.